1. Technical Field
The present invention relates to a vibrating element and a vibrating device, an electronic apparatus, and a moving object using the vibrating element.
2. Related Art
Recently, as crystal oscillators used for electronic apparatuses and automobile as moving objects or vibrating elements used for vibrating devices including angular velocity sensors, the following elements have been known.
For example, a vibrating element disclosed in Patent Document 1 (JP-A-2011-216924) is a tuning-fork vibrating element including a plurality of vibrating arms, and has a base part having a thickness in a Z-axis direction and two vibrating arms extending from the base part in a Y-axis direction and provided in parallel in an X-axis direction, with groove portions respectively dug into front surfaces and rear surfaces for improvement in vibration efficiency. Further, excitation electrodes are formed on the respective vibrating arms (drive arms). In the vibrating element, the two vibrating arms are vibrated in plane in the X-axis directions when voltages are applied to the above described electrodes formed on the vibrating arms.
Further, a vibrating element disclosed in Patent Document 2 (WO 2010/047115) is a tuning-fork vibrating element that detects an angular velocity and has a plurality of vibrating arms (drive arms). The vibrating element has a base part and two vibrating arms extending from the base part in a Y-axis direction in parallel to each other and provided in parallel in an X-axis direction. The respective vibrating arms have grooves respectively formed on front surfaces and rear surfaces opposed in a Z-axis direction, and their section shapes are “S”-shapes. The respective vibrating arms are formed in the shapes, and thereby, fluctuations of the Q-value may be suppressed while the mechanical strength is maintained.
The above described vibrating element may be formed by processing a plate-like substrate of e.g., crystal or silicon in a desired shape. Specifically, masks corresponding to the shapes in the plan view of the vibrating element are formed on both sides of the substrate and the substrate is etched via the masks, and thereby, the vibrating element may be obtained.
However, in the above described vibrating element disclosed in Patent Document 1, it is necessary to dig the grooves from the respective front surfaces and rear surfaces of the vibrating arms (drive arms). Further, in the vibrating element disclosed in Patent Document 2, it is necessary to form the grooves on the front surfaces and the rear surfaces so that the shapes of the vibrating arms (drive arms) may have the “S”-shaped cross sections. Particularly, in order to form the “S”-shaped cross sections of the vibrating arms like those of the vibrating element disclosed in Patent Document 2, the grooves should be formed deeper and the groove widths should be suppressed for downsizing of the vibrating arms (vibrating element). It is difficult to process the grooves deeper while suppressing their widths and, for example, the grooves formed on the front surfaces may penetrate to the rear surfaces or open to the side surfaces to chip the side surfaces. Further, for digging the grooves from the respective front surfaces and rear surfaces and forming electrodes or piezoelectric members on the front surfaces and the rear surfaces, the processing process becomes complex and the number of steps of the processing increases. As described above, the vibrating element in related art has a problem that the larger number of steps are taken for formation of the vibrating arms having the grooves from the front and rear surfaces and processing is harder.
Here, the inventor of the application focuses on oblique vibration of the vibrating arms in a direction in which both vibration components in the Z-axis direction and the X-axis direction are synthesized by asymmetric cross section shapes of the vibrating arms (asymmetric with respect to the center line in the X-axis direction as the width direction of the vibrating arms) and proposes a vibrating element using the oblique vibration. Even in the vibrating element using the oblique vibration, for example, when the grooves are formed from the front and rear surfaces of the vibrating arms as in Patent Document 1 or Patent document 2, there is the above described problem that the larger number of steps are taken and processing is harder.